Solubility and Diffusivity: Important Metrics in the Search for the Root Cause of Light-and Elevated Temperature-Induced Degradation

Mallory A. Jensen*, Ashley E. Morishige, Sagnik Chakraborty, Romika Sharma, Hannu S. Laine, Barry Lai, Volker Rose, Amanda Youssef, Erin E. Looney, Sarah Wieghold, Jeremy R. Poindexter, Juan Pablo Correa-Baena, Tahina Felisca, Hele Savin, Joel B. Li, Tonio Buonassisi

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

19 Citations (Scopus)


Light-and elevated temperature-induced degradation (LeTID) is a detrimental effect observed under operating conditions in p-Type multicrystalline silicon (mc-Si) solar cells. In this contribution, we employ synchrotron-based techniques to study the dissolution of precipitates due to different firing processes at grain boundaries in LeTID-Affected mc-Si. The synchrotron measurements show clear dissolution of collocated metal precipitates during firing. We compare our observations with degradation behavior in the same wafers. The experimental results are complemented with process simulations to provide insight into the change in bulk point defect concentration due to firing. Several studies have proposed that LeTID is caused by metal-rich precipitate dissolution during contact firing, and we find that the solubility and diffusivity are promising screening metrics to identify metals that are compatible with this hypothesis. While slower and less soluble elements (e.g., Fe and Cr) are not compatible according to our simulations, the point defect concentrations of faster and more soluble elements (e.g., Cu and Ni) increase after a high-Temperature firing process, primarily due to emitter segregation rather than precipitate dissolution. These results are a useful complement to lifetime spectroscopy techniques, and can be used to evaluate additional candidates in the search for the root cause of LeTID.

Original languageEnglish
Pages (from-to)448-455
Number of pages8
JournalIEEE Journal of Photovoltaics
Issue number2
Publication statusPublished - 1 Mar 2018
MoE publication typeA1 Journal article-refereed


  • Carrier-induced degradation (CID)
  • light-and elevated temperature-induced degradation (LeTID)
  • light-induced degradation
  • materials reliability
  • multicrystalline silicon (mc-Si)
  • passivated emitter and rear cell (PERC)
  • silicon
  • synchrotron
  • X-ray fluorescence

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